Currently, cost efficient disk drives allow for deploying large amounts of accessible storage, for example, on line storage. Conventional mass storage systems may use, for example, a redundant array of independent disks (RAID) clusters as a disk cache, often with a file system interface. The disk cache may be backed up by tape libraries which serve as the final repository for data. In mass storage systems where performance is an issue, tape back up may serve only as a deep archive for disaster recovery purposes. Tape back up requires considerable time to retrieve and access if required by loss of primary data storage. If a high availability system is required, the data is often duplicated on a separate system, with a fail-over mechanism controlling access to the additional system.
Data storage devices, for example, computer hard drives, have a motor driven (spinning) hard disk drive connected to a disk spindle. Currently, disk drive spindles consume energy to enable them to spin continually so data access latency is minimized. If a disk drive is powered down or spun down, it takes a period of time, usually a certain amount of seconds, to power up or spin back up before data can be accessed. Some disk drives may contain data that is accessed infrequently, and this data may reside in a small subsection of the disk drive. However, typical application access protocol dictates that the disk drive must be accessible within sub 1 second latencies, therefore the disk drive must continue to spin to prepare for the eventuality of an access request. Therefore, a current solution for rapid access to disk drives is to keep all disk drives spinning continuously, especially in an enterprise environment. A drawback of continuous spinning disk drives is that power consumption is continuous and wear and tear on the disk drives is also continual.
For example, in a massive array of idle disks (MAID) configuration with caching a plurality of passive storage device, for example passive disk drives are in standby mode until needed. A fraction of the passive drives act as overhead, i.e., remains powered up, and thus this limits the potential energy savings of passive drives in standby mode. For example, an array of ten disk drives may include an additional active cache drive, the cache drive remains spinning at all times. Thus, the MAID cache configuration cannot save more than 90% of the energy of a system that is constantly active with 10 data drives.
It would therefore be desirable to provide a method, and system employing the method, for allowing fast access to data on a data storage device, such as a computer disk drive, while saving energy in powering the device, e.g., the disk drive. It would further be desirable for a data storage device such as a disk drive to be shut down, without adversely affecting data retrieval times.